ECD
Definition
Electron capture detector. A Ni-63 radioactive source produces a baseline electron current that is reduced when electron-affinic species (halogens, nitro groups, peroxides) sweep past. Exquisitely sensitive for organochlorine pesticides and nitroaromatic explosives.
- Radioactive source
- Nickel-63
- Primary forensic use
- Pesticide and explosive residue analysis
- Chromatography type
- Gas-liquid chromatography (GLC)
Common questions
What does ECD stand for and what does it detect?+
ECD stands for Electron Capture Detector. It's a specialized detector used in gas chromatography that is extremely sensitive to compounds containing halogens, nitro groups, and other electron-attracting molecules. This makes it especially useful for finding pesticide residues and explosive traces in forensic samples.
How does an ECD detector work?+
An ECD uses a radioactive nickel-63 source to produce a steady stream of electrons. When molecules that capture electrons (like organochlorine pesticides or nitroaromatic explosives) pass through the detector, they pull electrons out of that stream. This drop in electron current is measured and recorded, creating a signal for those compounds.
Why is ECD preferred for detecting pesticides and explosives?+
ECD is exceptionally selective and sensitive for halogenated compounds and nitro-containing molecules, which are the key components of many pesticides and explosives. This specificity allows forensic analysts to identify and measure these substances even in tiny amounts, making it ideal for residue analysis in forensic investigations.
Related terms
- FID
- Flame ionisation detector. A hydrogen-air flame ionises C-H bond containing analytes and a collector electrode reads the ion current. Near-universal for organic...
- Capillary Column
- A fused silica tube 15 to 60 m long with an internal diameter of 0.25 to 0.53 mm and a stationary liquid...
- Carrier Gas
- The inert mobile phase that sweeps the sample through the column. Helium is traditional and gives the best peak shape on capillary...
- Derivatisation
- A pre-injection chemical step that converts polar, non-volatile or thermally fragile analytes into volatile, GC-friendly derivatives. Silylation with BSTFA is the most...
- Headspace GC
- Gas chromatography in which the sample (blood, urine, vitreous) is sealed in a vial, equilibrated at a fixed temperature, and a portion...
- Isocratic vs Gradient Elution
- Isocratic means the mobile-phase composition stays constant through the run; simple, reproducible, but limited resolving power for wide-polarity mixtures. Gradient means the...
- Mobile Phase
- The solvent or mixture that flows over the stationary phase and carries analytes along. Polarity, viscosity and volatility set the separation; switching...
- MSD
- Mass Selective Detector. GC-MS or LC-MS detector that identifies analytes by mass spectrum. The confirmation standard for drug and toxicology casework.
- Partition vs Adsorption
- Partition chromatography separates by differential solubility between two liquid phases (GLC, reversed-phase HPLC). Adsorption chromatography separates by surface binding to a solid...
- Plate Theory
- Model that treats a column as a series of theoretical plates. The Height Equivalent to a Theoretical Plate (HETP) measures column efficiency;...
- Rf Value
- The retention factor, defined as the distance the spot travels divided by the distance the solvent front travels on the same plate....
- Stationary Phase
- The immobile material the mixture flows past. In paper it is water inside cellulose fibres; in classical column work and TLC it...
Explained in these topics
- Chromatographic Techniques in Forensic Science: TLC, GLC, HPLC and HPTLCElectron Capture Detector. GLC detector selective for halogenated and other electron-affinic compounds. Workhorse for pesticide and explosive residue analysis.
- Gas-Liquid Chromatography (GLC): Columns, Carriers and DetectorsElectron capture detector. A Ni-63 radioactive source produces a baseline electron current that is reduced when electron-affinic species (halogens, nitro group...